As part of its “Sugar Smart campaign”, Change4Life has launched a free app that allows people to scan the barcode of a product to reveal the amount of sugar it contains in cubes and grams. It warns that obesity and tooth decay are among the consequences of children consuming three times as much of the substance as they should.

Dr Alison Tedstone, chief nutritionist for Public Health England, said: “Children are having too much sugar. This can lead to painful tooth decay, weight gain and obesity, which can also affect children’s wellbeing as they are more likely to be bullied, have low self-esteem and miss school.

“Children aged five shouldn’t have more than 19 grams of sugar per day – that’s five cubes, but it’s very easy to have more. Our easy-to-use app will help parents see exactly where the sugar in their children’s diet is coming from, so they can make informed choices about what to cut down on.”

The maximum added sugar intake for seven- to 10-year-olds is 24g, or six sugar cubes; for anyone aged 11 or older, it is 30g or seven sugar cubes.

The campaign will include television, digital and outdoor advertising, and five million Sugar Smart packs will be given away to primary schoolchildren and their families via schools, local authorities and retailers.